The kinematics of upper extremity reaching: a reliability study on people with and without shoulder impingement syndrome

Abstract

Background: Tasks chosen to evaluate motor performance should reflect the movement deficits characteristic of the target population and present an appropriate challenge for the patients who would be evaluated. A reaching task that evaluates impairment characteristics of people with shoulder impingement syndrome (SIS) was developed to evaluate the motor performance of this population. The objectives of this study were to characterize the reproducibility of this reaching task in people with and without SIS and to evaluate the impact of the number of trials on reproducibility.

Methods: Thirty subjects with SIS and twenty healthy subjects participated in the first measurement session to evaluate intrasession reliability. Ten healthy subjects were retested within 2 to 7 days to assess intersession reliability. At each measurement session, upper extremity kinematic patterns were evaluated during a reaching task. Ten trials were recorded. Thereafter, the upper extremity position at the end of reaching and total joint excursion that occurred during reaching were calculated. Intraclass correlation coefficient (ICC) and minimal detectable change (MDC) were used to estimate intra and intersession reliability.

Results: Intrasession reliability for total joint excursion was good to very good when based on the first two trials (0.77<ICC<0.99), and very good when based on either the first or last five trials (ICC>0.92). As for end-reach position, intrasession reliability was very good when using either the first two, first five or last five trials (ICC>0.82). Globally, MDC were smaller for the last five trials. Intersession reliability of total joint excursion and position at the end of reaching was good to very good when using the mean of the first two or five trials (0.69<ICC<0.95), and very good when using the mean of the ten trials (ICC>0.82). For most joints, MDC were smaller when using all ten trials.

Conclusions: The reaching task proposed to evaluate the upper limb motor performance was found reliable in people with and without SIS. Furthermore, the minimal difference necessary to infer a meaningful change in motor performance was determined, indicating that relatively small changes in task performance can be interpreted as a change in motor performance.

Figure 1

Starting position for the reaching movement. The reaching movements started with the upper extremity in a neutral position at the side of the body and the tip of the second finger in contact with a pressure switch. The kinematic was characterized using an optoelectric system and infrared light-emitting diodes positioned on five upper limb landmarks. As seen on the Figure, electromyography activity was also recorded, but the data were not analyzed in this study.

Figure 2

Position at the end of reaching in the frontal plane. The target was located in the frontal plane and positioned at a distance equivalent to the subject's arm length and at a height equivalent to the position of the second finger when the shoulder is at 90° of abduction. The kinematic was characterized using an optoelectric system and infrared light-emitting diodes positioned on five upper limb landmarks. As seen on the Figure, electromyography activity was also recorded, but the data were not analyzed in this study.

Figure 3

Intrasession intraclass correlation coefficients (ICC). The ICCs and its 95% confidence interval are presented for the first two trials, the first five trials and the last five trials out of ten in healthy subjects (n = 20) and for the last five trials in subjects with SIS (n = 30). The ICC are only presented for the last five trials in the SIS groups since the ICC were similar for the subjects with and without SIS. * Significant differences (P < 0.05) between the first two trials and the last five trials for healthy subjects.

Figure 4

Intrasession standardized error of measurement (SEM). The SEM and its 95% confidence interval are presented for the first two trials, the first five trials and the last five trials out of ten in healthy subjects (n = 20) and for the last five trials in subjects with SIS (n = 30). The SEM are only presented for the last five trials in the SIS groups since the SEM were similar for most joints in subjects with and without SIS. * Significant differences (P < 0.05) for the first two trials and the first five trials compared to the last five trials for healthy subjects. ^¶Significant differences (P < 0.05) between healthy subjects and the subjects with SIS.

Figure 5

Intersession intraclass correlation coefficients (ICC). The ICCs and its 95% confidence interval are presented for the mean of the first two trials, the first five trials and all ten trials in healthy subjects (n = 10).

Figure 6

Intersession standardized error of measurement (SEM). The SEM and its 95% confidence interval are presented for the mean of the first two trials, the first five trials and all ten trials in healthy subjects (n = 10).